Reservoir flow modelling to constrain CO2 plume-fault interaction. South West Hub Carbon Capture and Storage Project, WA

Summary

In order to improve the South West Hub Carbon Capture and Storage (SW Hub) site characterisation and reduce uncertainties around CO₂ capacity, injectivity and containment, conceptual fault hydrodynamic models are defined and numerical simulations are carried out to investigate the impact of faults on CO₂ plume distribution. These simulations model a worst case scenario with a plume reaching the interface between the top of the proposed injection unit and a secondary containment unit. The conceptual fault hydrodynamic models are defined to incorporate host rock and fault properties accounting for fault zone lithology, cementation, and cataclastic processes.

Numerical flow simulations of CO₂ injection are performed to quantify cross- and up-fault migration of CO₂ in case of plume-faults interaction. Here CO₂ is intentionally injected close to a fault and >1,000 m shallower than the proposed large-scale injection depth, to force the supercritical CO₂ to reach the discontinuity and the interface between injection and a secondary containment unit.

Results show that if a CO₂ plume reaches the top of the injection unit none of the compartment bounding faults in the SW Hub would critically control CO₂ flow nor would they act as primary leakage pathways. CO₂ flow at the top of a faulted injection unit is primarily controlled by the sedimentological morphology of the secondary containment unit.

• CCS
• fault seal
• reservoir flow modelling